The great radiator debate

Published: 03 January, 2014

Nick Whitwell, managing director of Quinn Radiators, gives an overview of the current issues in the radiator market, including the ongoing debate about the benefit of radiators vs. underfloor heating and their compatibility with renewable energy sources.

The increasing use of low-temperature systems and renewable sources such as heat pumps has led to widespread industry debate about their compatibility with radiators, due to lower flow temperatures. This has seen the emergence of some industry myths surrounding the excessive size of radiators that need to be fitted and the benefit of other heat emitters such as underfloor heating (UFH).

Merchants should be aware of this and make sure they are armed with the proper facts, so that they can give customers the right advice about radiators, UFH and their compatibility with renewable and other low-temperature energy sources. This will become increasingly important as renewable installations are expected to increase over the next two years, due to the introduction of the government’s Renewable Heat Incentive scheme in spring 2014.

The most important message merchants can convey to customers is that radiators are suitable for use with low-temperature systems, but getting the right model is critical for the best system performance.

Renewable sources provide water at a much lower temperature than traditional boilers, typically between 45°c and 50°c. Therefore, heating systems driven by a renewable source will usually only operate at a Delta T of 20-25K, whereas a traditional boiler system would run at around Delta T 50K and condensing boilers at Delta T 40K. This means that the water in the radiators doesn’t get as hot with a low-temperature system, so the heat output is less and you will need a larger surface area from your emitter to get the room to a comfortable temperature.

It is not true, however, that the only solution is to use significantly larger radiators or a different type of heat emitter with a larger surface area, such as UFH. However, to be effective, the radiator needs to make optimum use of the water’s energy content. Therefore, the answer is actually to use a radiator with a higher heat output, a slightly larger surface area and low water content. This means that, while there may still be a small degree of increased size, you don’t need scale up to such a large radiator as many believe, or install other expensive heat emitters.

Double- or triple-panel options

An alternative idea with renewable systems is to get more radiator surface area in less wall space by using a triple panel or vertical radiator. By doubling or tripling up on the number of panels, it is possible to achieve higher heat levels from shorter radiators.

There are many benefits of installing radiators rather than UFH as the main heat emitter for renewable systems. First of all, assuming the heating system has been properly installed, no maintenance is required. Being on the wall, the heat emitted by radiators isn’t affected by coverings – unlike UFH where the heat emitted can vary depending on the floor coverings used.

Evidence also suggests that buildings heated by low temperature radiator systems consume less total energy than buildings with UFH, even when using renewable energy such as heat pumps. Last, but certainly not least, is cost – fitting a UFH system is much more expensive than installing radiators, particularly as most systems won’t provide a total heating replacement either.

A mistake often made is to install a renewable system or condensing boiler without replacing old radiators. Having older, less efficient radiators means the new boiler or renewable system will not be working as efficiently as it could be and the radiators would not have sufficient capacity to heat the room. In fact, a renewable system operating at a Delta T of 25K would need around two and a half times the heat output than was given by the old, original radiator.

One thing to note is there are still many households that have older, less efficient radiators in use. Many of these radiators do not have convectors and occupy a large wall space. In order to optimise the efficiency of radiators, surface area is key. It is for this reason that older-style radiators, especially those without convectors, naturally emit significantly less heat when compared with a modern radiator with convectors. Additional output gains in excess of 330% can be achieved when comparing old and modern radiators occupying the same wall space.

The most important message for merchants to communicate is that with all renewable systems, there will need to be some degree of increased output – width, height or depth – but there are different options available and you certainly don’t need to have a radiator as a wall. As long as you remember the golden rules of high (output) and low (water content) then heat emitters with huge surface areas aren’t needed, and any oversizing can be kept to a minimum.

Quinn Radiators’ heat loss calculator is now available as an app for smart phones or tablets, as well as on the website, to help find the right size radiators for both renewable and traditional systems.

This article first appeared in the October 2013 issue of Builders' Merchants News.

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